As wireless applications are becoming increasingly widespread, people have a more urgent demand for a communication bandwidth and network reliability. In a current Wireless Fidelity (WiFi) standard, a data throughout provided by an 802.11a/b/g technology no longer meets an increasing demand. Therefore, to provide a higher data throughout, an Institute of Electrical and Electronics Engineers (IEEE) working group issues the 802.11n standard, which increases a WiFi transmission speed from current 54 Mbps provided by the 802.11a standard and the 802.11g standard to 300 Mbps, or even up to 600 Mbps.
As everyone knows, the most direct method for increasing a network capacity is to increase a communication bandwidth. However, by using a conventional wireless technology, data can only be transmitted on one channel (a frequency bandwidth of the channel is 20 MHz) selected from several channels with a 20 MHz frequency bandwidth each. It is noteworthy that, in the 802.11n standard, a channel binding technology is introduced, that is, two adjacent 20 MHz channels are combined, so that a communication bandwidth is doubled. However, there are only three non-overlapped 20 MHz channels in 2.4 GHz WiFi. Therefore, in the 802.11n standard, a maximum of two 20 MHz channels can be bound, to form a 40 MHz channel resource. Because more channels are available on a 5 GHz frequency of WiFi, the IEEE further optimizes the 802.11n standard by using the 802.11ac standard that is applicable to the 5 GHz frequency band, that is, a bandwidth of bound channels is increased from 20 MHz and 40 MHz in the 802.11n standard to 80 MHz, or even to 160 MHz. In this way, an available spectrum becomes wider, and available channels also consecutively increase.
In the prior art, the 802.11ac standard defines an enhanced request-to-send (RTS)/clear-to-send (CTS) protocol based on the channel binding technology, which have the following two aspects of characteristics: In one aspect, during data transmission, a bandwidth needs to be selected from several fixed bandwidths, including 20 MHz, 40 MHz, 80 MHz, and 160 MHz, and the selected bandwidth includes bandwidth of a primary channel; in the other aspect, no matter how large the selected transmission bandwidth is, the entire bandwidth can only serve as bandwidth of one channel to transmit a piece of data, which is specifically: A sending end duplicates, within an available bandwidth (assuming that the available bandwidth is 80 MHz, and four 20 MHz bound channels are included), an RTS frame three times in a unit of 20 MHz, and in this case, the 80 MHz bandwidth is all occupied, and RTS frames are sent on the 80 MHz bandwidth, that is, four RTS frames are sent on four 20 MHz channels at the same time; afterwards, a receiving end detects a channel and a bandwidth that are available to the receiving end; if a part of the available bandwidth is being used, the receiving end only replies to, on the other part of the available bandwidth that is not being used, the sending end with a CTS frame, and reports the currently available bandwidth of the receiving end in the CTS frame (if the currently available bandwidth is 40 MHz, the 40 MHz bandwidth needs to include the bandwidth of the primary channel); the sending end sends a piece of data on the 40 MHz bandwidth, and then the receiving end replies with a block acknowledgment (Block ACK, BA) frame on a corresponding channel, so that the sending end confirms whether the data is successfully transmitted.
However, although time used for transmitting the data is shortened in the prior art, robustness of the data transmission cannot be improved, and during the data transmission, the bandwidth that includes the bandwidth of the primary channel needs to be selected from the several fixed bandwidths, which limits channel use flexibility.